1. Field of the Invention
The present invention relates to a dielectric ceramic composition.
2. Description of the Related Art
Recently, a high-frequency band referred to as “quasi-microwaves” of about several hundred MHz to several GHz is used for mobile phones and other such mobile communication devices whose demand is increasing. Thus, there is demand for devices having high-frequency properties as an electronic device, such as a filter, resonator, capacitor and the like, which is used in mobile communication devices. Further, with the decreasing size of recent mobile communication devices, there is also a need to reduce the size of high-frequency devices.
To contribute to the reduction in size of such high-frequency devices, surface mount devices (SMDs), which internally have a conductor such as an electrode, wires and the like (hereinafter, a conductor such as an electrode, wires and the like included in the interior of a high-frequency device is referred to as an “internal conductor”) have become mainstream.
Further, to lower the cost of the devices, it is desirable to use as the internal conductor a conductor which has a low-resistance and is inexpensive, such as Ag. Various conductor compositions have been proposed for dielectric ceramic compositions having low-temperature sintering properties which allows Ag to be used as an internal conductor. For example, materials having a BaO-rare earth oxide-TiO2-based compound as a main component have a high relative permittivity (∈r), a large Q value, and small resonant frequency temperature coefficient (τf). Thus, such materials are being a widely researched.
For example, research is being conducted into a technology to produce a device with improved properties by simultaneously firing the above-described dielectric ceramic having a high relative permittivity and a dielectric ceramic having a lower relative permittivity, which has different material qualities.
For example, Japanese Patent No. 3940424 (JP3940424B), Japanese Patent No. 3940419 (JP3940419B), and Japanese Unexamined Patent Application Publication No. 2006-124270 (JP2006-124270A) describe dielectric ceramic compositions having a BaO-rare earth oxide-TiO2-based having low-temperature sintering properties as a main component so as to enable Ag or an alloy having Ag as a main component to be used as an internal conductor.